The present invention relates to data processing tape drive apparatus. Specifically, a new air bearing is provided which avoids during accelerations and decelerations of the tape medium the formation of an air seal between the tape medium and the bearing surfaces.
Large scale data processing systems have, in the past, utilized magnetic tape as a data storage medium wherein the tape is wound and rewound between reels. The tape medium is guided into and out of a READ, WRITE head by bearings which, in the past, have provided an interface of forced air with the tape medium to lower friction forces and permit rapid acceleration and deceleration of the tape medium. The pressurized air bearings provide for a change in direction of the magnetic tape while avoiding contact between the bearing and tape.
Although air bearings have proven to be advantageous in high speed data processing tape transports, problems arise during rapid acceleration and deceleration of the tape medium. The tape medium edges have been known to form a seal with the air bearing surface. A change in air pressure and flow at the bearing surface results from the seal. The release of the air seal will cause a fluttering of the tape medium which will be conducted through the tape to other areas of the tape transport. Further, the tape being wound on the reel will form layers with uneven edges, interfering with subsequent payout of the tape during a direction of movement reversal common in start-stop operations.
The air bearings used in the prior art also permit oscillations to occur under stationary tape conditions if the tape bumps against the bearing surface. The air pressure increases and is released over the edge of the tape, causing the tape to vibrate or flutter, transmitting the vibration to other portions of the machine.
In view of the foregoing, an improvement to air bearings according to the present invention has been devised.